Preheat oven to 350 degrees F. Line 2 muffin tins with 18 paper liners; set aside. Meanwhile, prepare your cake batter: combine the cake mix, egg whites, oil, water, and cotton candy flavoring with an electric mixer until smooth, about 2 minutes. Divide the batter evenly among two bowls and tint each bowl with your desired shade of blue and pink (I only did one drop of coloring per bowl for a more pastel look).
Evenly distribute the colors among each muffin cup, filling about 3/4 full. Don't swirl the batters, just layer them. Swirling the batters together may muddy the colors.
Bake for approx. 15-18 minutes or until a toothpick inserted near the center comes out clean or with moist crumbs. Cool completely.
For the frosting, cream the butter, cotton candy flavoring and vanilla extract together in the bowl of a stand mixer until smooth, about 1 minute. Gradually add in the confectioners' sugar, about one cup at a time, alternating with little streams of the heavy cream until the frosting is light and fluffy. Divide the frosting evenly among two bowls and tint each bowl with blue and pink until your desired shade has been achieved. (Again, I did one drop of each color).
Using a pastry bag fixed with your desired tip, spoon some of the blue frosting down one side of the pastry bag. Spoon some of the pink frosting down the other side of the bag. It's okay if the frosting colors mix toward the tip portion of the bag; it'll just turn purple :)
Pipe the frosting onto the cooled cupcakes and top with a sprinkling of blue and pink sanding sugar. To make the cotton candy sticks, rip off a small piece of cotton candy and attach it to the wet end of a popsicle stick (just stick the popsicle stick tip in a little water). Serve immediately with the cotton candy sticks, but keep in mind- cotton candy, once exposed to air, hardens quickly. It's best to make the cotton candy sticks immediately before serving.